https://www.jool.mx/en/debian.html

apt install linux-headers-$(uname -r)
apt update
apt install jool-dkms jool-tools
sysctl -w net.ipv4.conf.all.forwarding=1
sysctl -w net.ipv6.conf.all.forwarding=1

modprobe jool
jool instance add "default" --iptables --pool6 64:ff9b::/96
ip6tables -t mangle -A PREROUTING -j JOOL --instance "default"
iptables -t mangle -A PREROUTING -j JOOL --instance "default"